[ANSWERED] Measuring a visible trail of color?

[Eva]

Hi there,
I am tracing a person through a camera and leaving a trail on a screen/projector with a 3D-particle actor.
I thought it could be interesting, if there is a certain point, when the trail/the white color on the screen e.g. is taking up a certain amount of space, then I would like to trigger something happening. It could be a change of light.
Is there a way to do that?
Good ideas are welcome:)
Eva

[jfg]

@Eva

you can use "Calc Brightness" or " Measure Color" actor.

Best regards, 

Jean-François

[dbini]

@eva

the Calc Brightness actor will give you realtime feedback of the average brightness of the pixels in a video stream.

you can use it to measure certain parts of the screen by cropping and zooming to those areas.

or you can use a Chroma Key to separate out specific colours, or a range of colours, to measure the amount of the trail.

there's also the Measure Color actor, which may be useful if you are using colours in your particles.

[Eva]

@dbini

Ah yes, I see, I use Get Stage Image, and the the Calc Brightness. Great, thanks! it seems to work.